Read the section on ground balance a couple time and practice. I have seen articles that put in in terms like a volume knob. When lowering the coil, if the threshold increase, then turn the GB knob CCW. If it decreased, then turn the GB knob CW. Just like a volume knob, CW to increase and CCW to decrease. One you get the hang of it, you will quickly get the machine ground balanced and will get to the point where you will do this automatically and not really think about it. After awhile it becomes automatically natural in operating the machine.
As for accessories, the 575 coil in trash areas may or may not make the difference in hunting that spot or moving on to a cleaner area. Good Luck.